1. Field of the Invention
This invention relates to electronic devices that use dielectrics.
2. Discussion of the Related Art
Cuprates are crystalline materials with complex unit cells that contain copper-oxygen planes. Such materials often have quasi-one or quasi-two dimensional structures. Exemplary quasi-one dimensional cuprates include cuprate ladder materials. Exemplary quasi-two dimensional cuprates include high-temperature superconductors.
FIG. 1 is a perspective view along the c-axis of a generic cuprate ladder material 10. The cuprate ladder material 10 has the form of a stack along the crystal""s b-axis. The stack includes alternating Cu2O3 sheets 12 and CuO2 chains 14. The Cu2O3 sheets 12 and CuO2 chains 14 are separated by rows of atoms 16 whose relative percentages are determined by the crystal""s stoichiometry. For a crystal with the stoichiometry (Sr14xe2x88x92xCax)Cu24O41, the atoms 16 are Sr and/or Ca atoms.
FIGS. 2a, 2b, and 2c are side views of the Cu2O3 sheets 12, CuO2 chains 14, and rows of Sr, Ca 16 of one unit cell 18 of cuprate ladder material 10 of FIG. 1. The Cu2O3 sheets 12 include a ladder-like building block 19 of copper (light circles) bonded to oxygen (dark circles). In the Cu2O3 sheets 12, copper-oxygen ladders 19 link together via oxygen linkages. The CuO2 chains 14 also have a building block 20 of copper bonded to oxygen. In the unit cell 18, the Cu2O3 sheet 12 and CuO2 chain 14 have an almost commensurate structure in which seven blocks 19 match to ten blocks 20 along the c axis.
FIGS. 1, 2a-2c show that copper-oxygen ladders 19 define an anisotropy axis for the crystalline cuprate ladder material 10. The anisotropy axis is referred to as the c-axis. Due to the copper-oxygen ladders 19, cuprate ladder materials behave as quasi one-dimensional (1D) materials. Many such cuprate ladder crystals are 1D anti-ferromagnets with 1D lattice directions along the c-axis. It is believed that the copper-oxygen ladders cause the cuprate ladder crystals to behave as anti-ferromagnets.
Herein, a quasi-1D material has a strong anisotropy along a selected lattice axis. In exemplary quasi-1D materials, conductivities or dielectric constants are, at least, three times larger along the selected axis than along the remaining lattice axes.
Various embodiments advantageously include dielectrics that are quasi one-dimensional (1D) materials. The quasi 1D materials may have charge or spin density wave state in which their dielectric constants have giant real parts. Some of these dielectric constants have giant real parts at room temperature and above.
In one aspect, the invention features a capacitor having two electrodes and a quasi 1D dielectric material disposed between the electrodes. The dielectric material has a charge or spin density wave state.
In another aspect, the invention features an antenna having first and second electrodes and a quasi 1D dielectric material. The electrodes are located adjacent portions of the dielectric material. The dielectric material has a charge or spin density wave state.